In recent years, electronic apparatuses have been sophisticated and diversified. The tread is accompanied by an increase of electronic apparatuses in which an input device such as an optically transparent touch panel is mounted on the front surface side of a display device such as a liquid crystal display (LCD) and via this input device, a user recognizes and selects texts, marks, symbols or the like displayed on the display device, thereby switching functions of the electronic apparatus.
Such a conventional input device is described hereinafter with reference to FIG. 7 to FIG. 9 on an optically transparent touch panel (hereinafter referred to as touch panel) as an example.
FIG. 7 is an exploded perspective view showing a conventional touch panel. Touch panel 700 includes optically transparent upper substrate 81 made from polyethylene terephthalate, polycarbonate film, or the like. Upper substrate 81 has, for example, a rectangular shape. On substantially the entire surface of one principal surface of upper substrate 81, upper conductive layer 82 made from indium tin oxide, tin oxide, or the like, is formed by, for example, vacuum spattering.
A pair of upper electrodes 83 and 84 formed by printing paste such as silver or carbon are disposed, for example, along the outer circumferences of short side 81S and long side 81L of upper substrate 81. Upper electrodes 83 and 84 are formed by using silver or carbon in a portion in which a part of upper conductive layer 82 has removed by etching or laser-cutting. Upper electrodes 83 and 84 at one end are disposed on boundary portion 81LS of long side 81L and short side 81S of upper substrate 81, extend therefrom to central portion 81LC of long side 81L and coupled to upper lead parts 83A and 84A at another end, respectively. In the vicinity of upper lead parts 83A and 84A, dummy lead parts 83B and 84B are disposed.
Furthermore, optically transparent lower substrate 85 made from acrylic resin, poly-carbonate resin, or the like, is disposed facing upper substrate 81 and includes optically transparent lower conductive layer 86 on substantially the entire surface of one principal surface of lower substrate 85, similar to upper conductive layer 82.
A pair of lower electrodes 87 and 88 are formed by using silver or carbon in a portion from which a part of lower conductive layer 86 has removed by etching or laser-cutting. One ends of lower electrodes 87 and 88 extend to substantially central part 86LC of long side 86L of lower substrate 85, and are coupled to lower lead parts 87A and 88A, respectively. In the vicinity of lower lead parts 87A and 88A, dummy lead parts 87B and 88B are disposed.
Lower conductive layer 86 has a plurality of dot-spacers (not shown) on its one principal surface for maintaining predetermined space between upper conductive layer 82 and lower conductive layer 86. The dot spacers are formed at predetermined intervals and made from insulating resin such as epoxy or silicon.
Furthermore, frame-like spacer 89 having adhesive applied to its upper and lower surfaces is provided on one principal surfaces of upper and lower substrates 81 and 85. Upper conductive layer 82 and lower conductive layer 86 are bonded at their outer circumferences with spacer 89 so that upper conductive layer 82 and lower conductive layer 86 face each other with predetermined space maintained therebetween. Between upper substrate 81 and lower substrate 85, flexible wiring board 10 is inserted to be held. Flexible wiring board 10 includes a plurality of wiring patterns, electrodes and connectors formed on both surfaces of the substrate as described below.
FIG. 8 is an enlarged view showing wiring board 10 shown in FIG. 7. At the side of one end 10R of one principal surface of wiring board 10, a plurality of electrodes 12B to 15B are disposed at substantially the same intervals. Electrodes 12B to 15B are coupled to one ends of wiring patterns 12 to 15, respectively. Connectors 12A to 15A are coupled to the other ends of wiring patterns 12 to 15. With such a configuration, electrodes 12B to 15B and connectors 12A to 15A are located at the most distant places from each other on wiring board 10.
Wiring patterns 12 and 14 extending from electrodes 12B and 14B extend on one principal surface of wiring board 10 and are directly coupled to connectors 12A and 14A, respectively. On the other hand, wiring patterns 13 and 15 extending from electrodes 13B and 15B pass through through-holes 13C and 15C, which are formed by filling a conductive agent to holes piercing from one principal surface toward the other principal surface of wiring substrate 10, are coupled to wiring patterns 13D and 15D of the lower surface disposed on the other principal surface, and then extends to be coupled to connectors 13A and 15A provided on the other principal surface.
FIG. 9 is a sectional view showing conventional touch panel 700 shown in FIG. 7. On one principal surface of upper substrate 81, anisotropic conductive adhesive agent 11 is applied between lead parts of upper electrodes 83 and 84, and connectors of wiring board 10, and upper lead parts 83A and 84A of upper substrate 81 are coupled to connectors 12A and 14A on the upper surface and, lower lead parts 87A and 88A of lower substrate 85 are coupled to connectors 13A and 15A on the lower surface, respectively. Thus, touch panel 700 is constructed.
Note here that on upper substrate 81 and lower substrate 85, dummy lead parts 83B, 84B, 87B and 88B are disposed. Such dummy lead parts are provided in order to equalize the thickness between upper substrate 81 and lower substrate 85 when wiring board 10 is inserted to be held between upper substrate 81 and lower substrate 85, and the predetermined lead part and the connector are coupled to each other by heating and pressing treatment. Thus, both substrates can be pressed uniformly. Touch panel 700 is mounted on a front surface of a display device such as an LCD. Electrodes 12B to 15B provided at one end 10R of wiring board 10 are coupled to a detecting circuit of an electronic apparatus by coupling connectors (not shown) and the like.
When upper substrate 81 that is an operation surface of touch panel 700 is depressed by a finger, a pen, or the like, upper substrate 81 is bowed and upper conductive layer 82 corresponding to the depressed portion of upper substrate 81 is brought into contact with lower conductive layer 86. Then, the detecting circuit (not shown) applies voltage to a portion between upper electrodes 83 and 84 via connectors 12A and 14A as well as a portion between lower electrodes 87 and 88 via connectors 13A and 15A, respectively. From the applied voltage and electric current, a resistance component between each upper electrode and lower electrode is calculated. From the ratio of the resistance components of those electrodes, the depressed position is detected, thereby switching a function of the electronic apparatus to another function.
Resistance component Rx at the side of the upper electrode is detected at connectors 12A and 14A and resistance component Ry at the side of the lower electrode is detected at connectors 13A and 15A, respectively. The size of resistance component Rx and the size of resistance component Ry are sent to a detecting circuit, respectively, by electrodes 12B and 14B and electrodes 13B and 15B disposed on one end portion 10R of wiring board 10.
Information on prior art document relating to the invention of this application is disclosed in, for example, Japanese Patent Unexamined Publication No. 2003-108302.
However, in the above-mentioned conventional wiring board and the input device using the same, in the resistance components of the upper and lower electrodes, resistance component Rx at the side of the upper electrode on the upper surface is detected at connectors 12A and 14A on the upper surface and sent to a detecting circuit by electrodes 12B and 14B by way of wiring patterns 12 and 14 which extend as it is.
On the other hand, resistance component Ry at the side of the lower electrode on the lower surface is detected at connectors 13A and 15A on the lower surface and sent to a detecting circuit by electrodes 13B and 15B by way of wiring patterns 13 and 15 extending from wiring patterns 13D and 15D on the lower surface and changing the place to the upper surface through through-holes 13C and 15C.
In a conventional wiring board and touch panel, it is necessary to couple the connector of wiring board 10 corresponding to the place between the upper electrode and the lower electrode which face each other. Therefore, wiring board 10 has to be provided with wiring patterns both on one principal surface and the other principal surface of wiring board 10 and through holes. Consequently, there was a problem that a manufacturing process is increased, which makes an input device expensive.